BRPI0707890A2 - fluid catalytic cracking process for the preparation of cracked products - Google Patents

Abstract

FLUID CATALYTIC CRACKING PROCESS FOR THE PREPARATION OF CRACKED PRODUCTS. A fluid catalytic cracking process for the preparation of products cracked by contact in a reactor of a hydrocarbon feed load with a cracking catalyst, wherein the hydrocarbon feed load comprises a paraffin and triglyceride feed load.

Description

"FLUID CATALYTIC CRACKING PROCESS FOR PREPARING CRACKED PRODUCTS"

Field of the Invention

The present invention relates to a fluid catalytic cracking process.

Background of the Invention

In fluid catalytic cracking processes a preheated hydrocarbon feedstock from a high boiling point is contacted with a hot cracking catalyst in a catalytic cracking reactor, usually a rising pipe. Feed is cracked in lower boiling products such as dry gas, LPG, gasoline and unwanted liquid waste. In addition, coke and nonvolatile products deposit on the catalyst resulting in an exhausted catalyst. The reactor exits to a separator in which the depleted catalyst is separated from the reaction products. In the next step the depleted catalyst is extracted with water vapor to remove nonvolatile hydrocarbon products from the catalyst. The extracted catalyst is passed to a regenerator in which the coke and the remaining hydrocarbon materials are combusted and the catalyst is heated to a temperature necessary for cracking reactions. Here the hot regenerated catalyst is returned to the reactor.

As the hydrocarbon feedstock a feedstock comprising a large amount of paraffins may be reduced. However, cracking such a paraffin-rich hydrocarbon feedstock, such as, for example, a Fischer-Tropsch product, is not straightforward.

US-A-4684756 describes a process for preparing a gas catalyst fraction by fluid catalytic cracking of a Fischer-Tropsch wax as obtained in an iron catalyzed Fischer-Tropsch process. Gasoline yield is 57.2% by weight.

A disadvantage of the process disclosed in US-A-4684756 is that gasoline yield is relatively low.

EP-A-454256 describes a process for preparing lower olefins starting from a Fischer-Tropsch product by contacting this product with a ZSM-5 containing catalyst at a temperature between 580 and 700 ° C in a moving bed reactor at a catalyst to oil between 65 and 86 kg / kg.

WO-A-2004/106462 describes a process in which a relatively heavy Fischer-Tropsch product and a catalyst system comprising a catalyst, whose catalyst comprises an acidic matrix and a large pore molecular sieve, are brought into contact by providing a product. gasoline that has a high content of iso-paraffins and olefins, compounds that contribute greatly to a high octane index.

A disadvantage of processing such a paraffin feed in an FCC unit is that the amount of coke making is too small. The coke on the catalyst is removed by oxidation in a so-called FCC regenerator. In such a process step the catalyst temperature increases due to exothermic reactions and reaches a temperature which makes it suitable for use in the actual catalytic decaying step. If the coke content of the catalyst is too low, additional regenerative fuel needs to be added and this is obviously undesirable.

NL-A-8700587 describes water-free butter catalytic cracking of hydrocarbon products such as C4 gases and lighter gases, gasoline (C5- 216 ° C), light and unwanted liquid waste over a RE-USY type catalyst comprises a crystalline aluminum oxide matrix.

It is the object of the present invention to achieve a process that is better thermally balanced than prior art processes.

Summary of the Invention

It has now been found that the above feat can be accomplished by performing fluid catalytic cracking of the paraffin feedstock in the presence of triglycerides.

Accordingly, the invention provides a fluid catalytic decaying process for the preparation of cracked products by containing in a reactor a common cracking catalyst hydrocarbon feedstock, wherein the hydrocarbon feedstock comprises the feedstock of etriglyceride paraffins.

It has been found that by cracking a mixture of a paraffin and triglyceride feedstock is formed, plus coke is formed on the cracking catalyst. An additional advantage of blending the mixture is that a gasoline having a higher octane rating is obtained. The Applicant has also found that by choosing the correct balance between paraffin feed loading on the one hand and ostriglycerides on the other hand, a gasoline product having a sulfur content of less than 10 ppm, an aromatic content of less than 35% can be obtained. by volume, preferably less than 25% by volume and an octane index higher than 87. The triglycerides present in the hydrocarbon feedstock are cracked and the products formed result in better RON octane index of the total product.

Detailed Description of the Invention

Triglycerides are glycerides in which glycerol is esterified with three fatty acids. Preferably, the triglycerides being used in the process according to the invention comprise fatty acids wherein the fatty acid group is in the range of from 4 to 30 carbon atoms, the fatty acids most commonly being saturated containing 1, 2 or 3 double bonds. Triglycerides are the main constituent in vegetable oil, fish oil and animal fat.

Preferably, the hydrocarbon feedstock comprises vegetable oil, animal fat or fish oil to provide ostriglycerides. Vegetable oil, animal fat or fish oil need not be in anhydrous or pure form or subject to prior hydrogenation. The oil or fat may contain varying amounts of free fatty acids and / or esters, both of which may be converted to hydrocarbons during the process of this invention. The oil or fat may also comprise carotenoids, hydrocarbons, phosphatides, simple fatty acids and their esters, terpenes, sterols, fatty alcohols, tocopherols, polyisoprene, carbohydrates and proteins.

Vegetable oils include rapeseed oil, depot oil, coconut oil, corn oil, soybean oil, safflower oil, sunflower oil, flaxseed oil, olive oil and peanut oil. Suitable animal fats include pork fat, beef fat, meat fat and chicken fat. Mixtures of oils or fats from different sources can be used as feed for the catalytic conversion step. Thus, mixtures of vegetable oils, animal fats, fish oils and mixtures including vegetable oil, animal fat or fish oil may be used. Preferred oils are rapeseed oil and calming oil, in particular palm oil. The use of calming oil has been found to result in greater conversion to cracked products and higher gasoline yields.

The hydrocarbon feedstock may also comprise non-triglyceride natural fatty acids and esters, for example methyl fatty acid esters derived from the transesterification of vegetable oils and animal oils above. Unless one wishes to be bound by any theory, cracking has been found Triglyceride catalysis appears to be a stepwise process in which the first stage fatty acid molecules and the glycerol backbone are being formed. The fatty acid molecules are subsequently cracked providing lighter components. It has been found that, in the presence of a cracking catalyst, the conversion of triglycerides to fatty acids is almost instantaneous, whereas the next step, which is the conversion of fatty acids, depends on factors such as catalyst to oil ratio, catalyst type, temperature. and tempode residence.

Typically, oxygen present in triglycerides is expected to be converted to CO2 in the catalytic cracking step. However, it has been found that most oxygen is converted to water as a byproduct. This water will already function as an extraction gas and will be separated from the valuable products in the fluid catalytic cracking process extraction step.

Examples of suitable paraffin feed fillers are a hydrocarbon stream derived from Fischer-Tropsch or hydrowax.

Hydrowax is the bottom fraction of a hydrocracker. By hydrocracking in the context of the present invention is meant a hydrocracking process of which the principal products are typically naphtha, kerosene and diesel. The conversion, expressed as a percentage by weight of the feed fraction for the boiling point hydrocracker above 370 ° C to boiling point hydrocarbons below 370 ° C, is typically above 50% by weight. Examples of hydrocracking processes that can provide a bottom fraction that can be used in the present process are described in EP-A-699225, EP-A-649896, WO-A-97/18278, EP-A-705321, EP-A-994173 and US-A-4851109. By "Fischer-Tropsch-derived hydrocarbon stream" is meant that the hydrocarbon stream is a product derived from or derived from a Fischer-Tropsch hydrocarbon process product by a hydroprocessing step, that is, hydrocracking, hydroisomerization and / or hydrogenation.

The Fischer-Tropsch reaction converts carbon monoxide and hydrogen into longer chain, usually paraffin hydrocarbons:

n (CO + 2H 2) = (-CH 2 -) n + 1 H 2 O + heat,

in the presence of a suitable catalyst and typically at elevated temperature, for example 125 to 300 ° C, preferably 175 to 2500 ° C and pressure, for example 5 to 100 bar, preferably 12 to 80 bar. Hydrogen: carbon monoxide ratios other than 2 may be employed.

Carbon monoxide and hydrogen are typically derived from a partial oxidation hydrocarbon feedstock. Suitable hydrocarbon feedstocks include gaseous hydrocarbons such as natural gas or methane, mineral gas, biomass or residual fractions from crude oil distillation.

The Fischer-Tropsch-derived hydrocarbon stream may suitably be called a "gross synthetic" synthetic raw stream as described, for example, in GB-A-2386607, GB-A-2371807or EP-A-0321305. Other suitable Fischer-Tropscha hydrocarbon streams may be hydrocarbon fractions with naphtha, kerosene, diesel or wax range as obtained by the Fischer-Tropsch hydrocarbon synthesis process, optionally followed by a hydroprocessing step.

Preferably, the Fischer-Tropsch hydrocarbon stream product was obtained by hydroisomerization of hydrocarbons directly obtained in the Fischer-Tropsch hydrocarbon synthesis reaction. The use of a hydroisomerized hydrocarbon fraction is advantageous because it contributes to a high gasoline yield due to the high iso-paraffin content in said fraction. A 5-boiling hydroisomerized fraction in the kerosene or diesel range may suitably be used as the Fischer-Tropsch-derived hydrocarbon stream. Preferably, however, a higher boiling point hydroisomerized fraction is used as feed. A higher boiling point hydroisomerized hydrocarbon fraction is used as feed.

A particularly suitable hydroisomerized hydrocarbon moiety is a moiety having a boiling point T10 wt.% Of 350 to 450 ° C and a T90 wt.% Of 450 to 600 ° C and a wax ester of 5 to 60 wt.%. Such a fraction is typically termed waxy uncontaminated. Preferably, the wax content is between 5 and 30% by weight. Wax odor is measured by solvent removal of wax at -27 ° C in a 50/50 vol / vol mixture of methyl ethyl ketone and toluene. Examples of such hydrocarbon streams are the commercially available Waxy Refined product as sold by Shell MDS (Malaysia) Sdn Bhd snf waxy refined product as obtained by the process described in WO-A-02/070630 or EP-B-0668342.

The paraffin feedstock preferably comprises at least 50% by weight of paraffins, more preferably at least 70% by weight of paraffins. Paraffins are both normal and iso-paraffins. Paraffin contents of paraffin feed loads in the context of the present invention are measured by multi-dimensional comprehensive gas state chromatography (GCxGC) as described in P.J. Schoenmakers, J. L. Μ. M. Oomen, J. Blomberg, W. Genuit, G. van Velzen, J. Chromatogr. A, 892 (2000) p. 29 and others.

The hydrocarbon feedstock according to the present invention comprises both a paraffin feedstock and triglyceride feedstock. Preferably, the weight ratio of the amount of paraffin feedstock to the amount of glycerides present in the hydrocarbon feedstock is between 20: 1 and 1: 5, more preferably between 5: 1 and 1: 2.

The hydrocarbon feedstock may optionally also comprise a component that is not a triglyceride or paraffin feedstock. Suitable components are the so-called conventional FCC feed loads, which are typically crude oil refining derivatives and which are less paraffinic than the paraffinic feeds described above. The conventional FCC feedstock that can be used in the process according to the invention includes high boiling non-residual crude oil fractions such as vacuum oil, direct run (atmospheric) diesel, decoctor gas oils and atmospheric distillation residues, and These feed loads preferably have boiling points in the range from 220 ° C to 650 ° C, more preferably in the range from 300 ° C to 600 ° C.

The amount of conventional FCC feedstock relative to the paraffin and triglyceride feedload may vary depending on the availability of the feedstock and the desired product quality. In the process according to the invention the hydrocarbon feedstock may comprise up to 90% by weight of conventional FCC feedstock, preferably up to 70% by weight of conventional FCC feedload, more preferably up to 50% by weight of feedstock. conventional FCC, even more preferably up to 40% by weight of the conventional FCC feed load. An advantage of processing a conventional FCC feed filler mixture, the feedstock of ettriglyceride paraffins is, for example, that a gasoline with a reduced aromatic content is produced. Another advantage is that when triglycerides and a paraffin feed filler are added to a conventional FCC feed filler, a lower yield of lower olefins is obtained. The advantages of the present invention become less pronounced at a lower content of the conventional feed FCC feed load.

Thus, by choosing the right balance between paraffin and triglyceride feed loading on the one hand and conventional FCC feed loading on the other hand, a gasoline product can be obtained which has the desired properties such as a low octane acceptable content. sulfur and a desired aromatic content. The properties of cracked products can be adjusted.

In the process according to the invention, the decaying catalyst comprises a large pore zeolite. By a large pore zeolite is meant a zeolite comprising a porous, crystalline aluminosilicate structure having an internal porous cell structure over which the major pore axis is in the range of from 0.62 to 0.8 nanometer. Zeolite axes are represented in the "Atlas of ZeoliteStructure Types" by W.M. Meier, D.H. Olson and Ch. Baerlocher, Fourth Edition 1996, Elsevier, ISBN 0-444-10015-6. Examples of such large porezezeites are FAU or faujasite, preferably faujasitasynthetic such as zeolite Y, USY, Rare Earth Y (= REY) or Rare Earth USY (REUSY). According to the present invention USY is preferably used as the large pore zeolite.

The cracking catalyst preferably also comprises a medium pore zeolite if a high yield of polypropylene is desired. By a medium pore zeolite which may be used in the present invention is meant a zeolite comprising a porous, crystalline aluminosilicate structure having an internal porous cell structure over which the major pore axis is in the range of from 0.45 to 0.62 nanometer. Examples of such medium pore zeolites are structural type MFI such as ZSM-5, MTW type such as ZSM-12, structural typeTON such as theta one and structural type FER such as ferrierite. According to the present invention preferably ZSM-5 is used as the middle pore zeolite.

The weight ratio of large pore zeolite to medium pore zeolite in the cracking catalyst is preferably in the range from 99: 1 to 70:30, more preferably in the range from 98: 2 to 85:15.

The total amount of large pore zeolite and / or medium pore zeolite that is present in cracking catalysts is preferably in the range of from 5 to 40 wt%, more preferably in the range of 10 to 30 wt%, even more preferably. in the range from 10 to 25% by weight relative to the total mass of the catalyst.

Near the large or medium pore zeolite, the catalysts may comprise one or more porous binder materials of inorganic refractory demetal oxide or active matrix supports and / or materials. These binder materials or supports may or may not contribute to the decaying reaction. Examples of such binder materials are silica, alumina, titania, zirconia and magnesium oxide or combinations of two or more of the same. In addition organic binders may be used.

The temperature at which the hydrocarbon feedstock and cracking catalyst are contacted is preferably between 450 and 650 ° C. More preferably, the temperature is above 475 ° C, even more preferably above 500 ° C. Gasoline benefits are observed at temperatures above 600 ° C. However, temperatures above 600 ° C will give rise to thermal decay reactions and the formation of undesirable gaseous products such as methane and ethane. For this reason the temperature is preferably below 600 ° C.

The process can be performed on various types of reactors. To simplify catalyst regeneration, preference is given to a fluidized delight reactor or a reactor riser. If the process is carried out in a reactor riser, the preferred contacting time is between 1 and 10 seconds and more preferably between 2 and 7 seconds. The decatalyst to oil ratio (hydrocarbon feed load) is preferably between 2 and 20 kg / kg. It has been found that good results can be obtained at a catalyst to oil ratio above 6 kg / kg, as a larger catalyst to oil ratio results in a greater amount of decoction over the catalyst.

Examples

The invention is also illustrated by the following Examples. The most important hydrowax properties are given in table 1.

Table 1

<table> table see original document page 12 </column> </row> <table>

Example 1

Catalytic cracking experiments were performed in a rising microtube reactor operating in an isothermal weathered flow regime. The Rising Microtube Reactor is a bench-scale, single-pass catalytic fluid-cracking reactor that simulates hydrodynamics of an industrial FCC reactor. The temperature of the reactor was adjusted to 525 ° C. The reactor length was in these experiments 21.2 meters. The catalyst used was a commercial silica sol-based equilibrium FCC (e-cat) catalyst, which contains 11% by weight of USY zeolite crystals. Prior to each experiment, the catalyst was regenerated in a fluidized bed reactor, where coke was subjected to combustion in air at 600 ° C for three hours. The catalyst was fed to the reactor via a catalyst feeder. Nitrogen was used to facilitate catalyst flow. Oil supply was provided via a pulse-free syringe pump to the preheated oven where it was partially evaporated. In the last part before the injection point the oil was completely evaporated and the reaction temperature was adopted, as well as the catalyst. The feed was injected perpendicular to the catalyst current. The feed consisted of pure hydrowax or hydrowax mixed with 20 wt% or 40 wt% rapeseed oil from which gum was eliminated.

Sample collection began when the system had reached steady state operation. The separation of catalyst and product gas occurred by means of a cyclone. During steady state operation the catalyst was stored under reaction conditions and then extracted with nitrogen. The effluent gas was conducted through three series condensers operating at 25, -60 and -60 ° C, respectively. Any noncondensed products were captured in a gas balloon. C1-C4 hydrocarbon components in the gas balloons were determined by means of gas chromatography. The dragged C5 and C5 hydrocarbons were detected as two clusters separated by this analysis method and added to the gasoline fraction. The liquid product was analyzed by simulated distillation. This provided the product quantities have boiling range agglomerates: gasoline (C5-215 ° C), Lightweight Unwanted Liquid Waste (LCO, 215-325 0C) Heavy Unwanted Liquid Waste and Oil Slurry (HCO + SO, 325 + ° C). The coke in the catalyst was determined with a LECO C-400 carbon analyzer. The results are presented in table2.

Compared to 100% hydrowax, the addition of rapeseed seed oil (RSO) results in higher amounts of coke and LCO. In addition, a clear increase in the calculated RON for catalytically cracked hydrowax blend with 40% by weight is observed. of rapeseed oil compared to 100% hydrowax.

Table 2

<table> table see original document page 14 </column> </row> <table>

Example

In a small-scale fluidized bed reactor, hydrowax catalytic cracking mixtures with rapeseed and palm oil (at 5, 10, 25 wt%) were performed using equilibrium catalysts, e-cat2. The experiments were performed in a reactor in which 10 grams of the commercial e-catalyst were constantly fluidized with nitrogen. Depending on the cat / oil ratio an amount of 1.25 to 3.33 grams of oil was injected into the reactor. During extraction the liquid products were collected in glass containers (receptors) in a bath at a temperature of -15 ° C. The gas produced was analyzed online with gas chromatography. After extraction for 660 seconds, the amount of coke formed on the catalyst was determined by combustion of the catalyst coke in a regeneration step. For 40 minutes the reactor temperature was 650 C in an air environment. The coke was converted to CO2 and measured online. After regeneration the reactor was cooled to the reaction temperature and a new injection was started. The results are shown in tables 3 and 4.

Table 3. Product distribution using e-cat2 at 500 ° C (at a Cat / Oil ratio of 6.3) hydrowax (HWX) and hydrowax and rapeseed oil (RSO) mixtures.

<table> table see original document page 15 </column> </row> <table>

Table 4. Product distribution using e-cat2 at 500 ° C (at a Cat / Oil 6 ratio) of hydrowax (HWX) and mixtures of hydrowax and palm oil.

<table> table see original document page 15 </column> </row> <table>

Claims (11)

Fluid catalytic cracking process for the preparation of cracked products, characterized in that it contacts a hydrocarbon feedstock reactor with a decay catalyst, wherein the hydrocarbon feedstock comprises a paraffin and triglyceride feedload. A process according to claim 2, characterized in that the paraffin feedstock comprises at least 50 wt.% Paraffins, preferably at least 70 wt.% Paraparaffins. Process according to Claim 1 or 2, characterized in that the weight ratio of the paraffin feedstock to the triglycerides present in the hydrocarbon feedstock is in the range from 20: 1 to 1: 5 plus preferably from 5: 1 to 1: 2. Process according to any one of claims 1 to 3, characterized in that the hydrocarbon feedstock comprises up to 90% by weight of a conventional FCC feedload, more preferably up to 70% by weight. Process according to any one of claims 1 to 4, characterized in that the hydrocarbon feedstock comprises vegetable oil, preferably palm oil or seed oil. Process according to any one of claims 1 to 5, characterized in that the paraffin feed load is a hydrowax. Process according to any one of Claims 1 to 5, characterized in that the paraffin feed is a hydrocarbon stream derived from Fischer-Tropsch. Process according to any one of claims 1 to 7, characterized in that the cracking catalyst comprises a large pore size zeolite. Process according to claim 8, characterized in that the large pore size zeolite is USY. Process according to any one of claims 1 to 9, characterized in that the cracking catalyst comprises a medium pore size zeolite. Process according to claim 10, characterized in that the medium pore size zeolite is ZSM-5.